Takafumi Yao

TL;DR: In this article, the formation and optical properties of CdSe based, self-assembled quantum dot (QD) like nano-structures embedded in ZnSe have been studied.

Abstract: We have investigated electron-trap centers in ZnO layers grown under different Zn∕O flux ratios by molecular-beam epitaxy. Frequency-dependent capacitance measurements show that ZnO layers grown under Zn-rich and stoichiometric flux conditions suffer from larger dispersion than a ZnO layer grown under an O-rich flux condition. Temperature-dependent capacitance measurements reveal that all the ZnO layers have shallow electron-trap centers ET1 and deep electron-trap centers ET2, while the Zn-rich ZnO layer has another shallow electron-trap center ET3 besides ET1 and ET2: the thermal activation energies of ET1, ET2, and ET3 are estimated to be 0.033–0.046, 0.12–0.15, and 0.065 eV, respectively. Moreover, it is exhibited that the trap density of ET2 is larger than those of ET1 or ET3 in all the cases and increases as the Zn∕O flux ratio increases. Consequently, it is suggested that the large dispersion effect observed in the Zn-rich and stoichiometric ZnO layers is ascribed to the large density of deep electr...

TL;DR: In this paper, a significant role of refraction effect on reflection high-energy electron diffraction (RHEED) from nanostructures is demonstrated by kinematical calculations taking into account the refraction of electron beam at the curved surfaces of the dots.

TL;DR: In this paper, high-electron-mobility ZnO epilayers were grown on c-plane sapphire with double-buffer layers by plasma-assisted molecular beam epitaxy.

TL;DR: In this article, the lattice relaxation mechanism of ZnO films grown on c-Al2O3 substrates by plasma-assisted molecular-beam epitaxy was investigated by using both in situ time-resolved reflection high energy electron diffraction observation during the initial growth and absolute lattice constant measurements (Bond method) for grown films.